Slate is one of the finest roofing materials available and has several advantages over asphalt shingle roofs. Slate roofing is fireproof, resists hail damage, and often has a service life of 100 years or more. However, slate is a rigid natural stone product which unfortunately can be damaged by stress. Stress can be introduced into slate in several ways, but the most common cause of stress to slate is nails used to attach the slate to the roof deck. With nail installation, the nails need to be fastened so the slate hangs on the nail. If the nail is inserted too tightly, the nail will pinch the slate. On the other hand, if the nail is not inserted deep enough, the overlapping piece of slate may crack from the hidden pressure point. Environmental effects on the wood decking and nails may also contribute to the stress. Environmental changes such as swings in temperature and humidity can cause the decking to expand and contract. If the nails are in a bind in this situation, the slate can crack or fall.